World aluminium prices are down to four-year lows, while animal pelts are at their highest levels in 16 years, according to a bank report.

In the first fall for five months, New Zealand's key export commodity prices eased back 0.4 per cent in November, the ANZ Commodity Price Index shows.

Despite the dip, the index is still only 2 per cent down on the all-time high in world price terms, seen in April this year.

The split between rises and falls was nearly even. Global prices for seven commodities rose in the month and six fell.

In the key dairy sector, some product prices were up and others down, but still "hitting the high notes", ANZ economist Steve Edwards said. "But it is a bit of a mixed picture."

The biggest drop in November was for aluminium, down 4 per cent in November. New Zealand exports of aluminium are worth about $1 billion a year, most going to Japan and Korea.

Earlier this year, the Tiwai Point aluminium smelter company signed a new secret power deal with state-owned Meridian Energy, with the Government kicking in a $30 million subsidy to ensure the Southland plant continues to the end of 2017.

While New Zealand Aluminium Smelters got a cheaper power price, it would rise should the New Zealand price for aluminium lift above agreed but unspecified levels.

Yesterday, the London Metal Exchange price for aluminium was about US$1740 (NZ$2130) a tonne, around levels seen when the power deal was signed, and well down on the peak earlier this year of more than US$2100. That will put more pressure on the Southland smelter's majority owner Rio Tinto.

Overseas analysts recently estimated that as much as a third of the aluminium smelting industry was losing money. More smelter closures were expected, a metals analyst told the Financial Times late last week.

The heavily oversupplied world market was pushing prices ever lower and they could hit US$1700 a tonne in coming months.

Rio Tinto announced last week plans to close its Gove alumina refinery in the Northern Territory, with 1100 jobs on the line. Alumina is used in the production of aluminium.

In contrast to weak metal prices, the ANZ commodity index showed, the prices of animal pelts rose 5 per cent to a 16-year high. Raw-hide exports are worth about $400m a year, with tanned hides adding almost $200m more.

Pelt prices tend to move in tandem with wool prices, which were up to a two-year high, Edwards said. Skins prices fell dramatically after the global financial crisis, but were now recovering. Some of the hides went to the fashion industry in Europe and some to places like China for use in furniture and car seats.

Meanwhile, whole-milk powder prices fell 3 per cent and the world butter price was down 2 per cent.

There was a 3 per cent lift in skim-milk powder and a 2 per cent rise in cheese prices.

Lamb, beef and wool prices were all up 1.5 per cent in the month, while log prices were up 0.25 per cent.

In NZ dollar terms, the basket of commodity prices was up 0.4 per cent in the month because of a a falling kiwi. It fell against the US dollar and the British pound, but rose to a six-year high against the Australian dollar.

The kiwi was trading at US81.7c yesterday.

In NZ dollar terms, the basket of commodity prices is 2 per cent down on the recent peak in August.